Association of recombinant proteins rASP-2 and rTC24 from Trypanosoma cruzi as a vaccine strategy against Chagas disease induces a mixed Th1/ Th17 immune response.

Chagas disease is a globally widespread parasitic infection caused by the flagellated protozoan Trypanosoma cruzi. It is classified as a neglected tropical disease, primarily affecting impoverished and rural regions where access to diagnosis and treatment is limited. Although treatment for this disease is effective, it is restricted to the acute phase, during which diagnosis is more challenging, reducing cure rates. Consequently, prevention remains the most effective control method, and recombinant proteins offer a promising strategy for vaccine development. Specifically, the proteins ASP-2 and TC24 have demonstrated immunoprotective activity in various experimental models. This study aimed to characterize the immune response elicited by the combined use of recombinant ASP-2 (from the intracellular stage) and TC24 (from the bloodstream stage), seeking to promote a synergistic protective effect compared to the response generated by the proteins used individually. To evaluate this, recombinant proteins rASP-2 and rTC24 were used as vaccine formulations to immunize female BALB/c mice as follows: Group 1: Saline solution; Group 2: 25 µg of rTC24 + aluminum hydroxide; Group 3: 25 µg of rASP-2 + aluminum hydroxide; Group 4: 12.5 µg of rTC24 + 12.5 µg of rASP-2 + aluminum hydroxide. The humoral immune response assessed IgG antibody levels by indirect ELISA of animal sera collected on days 0, 21, and 42 of the experiment, while the cellular response was evaluated by collecting and culturing splenocytes, assessing cytokines IFN-γ, TNF-α, interleukins 1β, 4, 6, 12, 17, and Toll-like receptor 4, quantified by real-time PCR. The results indicated a significant antibody production in the group where the proteins were combined (G4) compared to the control group (G1) on days 21 and 42. A significant increase in antibody production was also observed in group G4 on day 42 when compared to both groups using the isolated proteins (G2 and G3). Conversely, the cellular response showed an increase in IFN-γ and interleukins 1β and 17 in Group D, while the isolated ASP-2 protein induced the expression of TNF-α, interleukins 4 and 12, and Toll-like receptor 4. Western blotting using T. cruzi lysate and pooled serum confirmed the ability of the antibodies to recognize native parasite proteins. In conclusion, the combined use of proteins from different parasite life stages proved advantageous, indicating the induction of a mixed cellular immune response, predominantly of the Th1 and Th17 profiles.